In recent years, electronic information equipment such as a computer or a mobile phone, which enables an input operation utilizing a display of a display device, has been developed. A touch panel (also called a touch sensor) used in combination with a display device is installed as an input device in such electronic information equipment.
There are various forms of touch panels, such as the resistive film type, surface acoustic wave type, and infrared type touch panels. However, touch panels of capacitive type (hereinafter, also referred to as capacitive touch panels), which are excellent in terms of durability or the like, are generally used. Such capacitive touch panels have a plurality of electrodes arranged on an input operation surface (hereinafter, also simply referred to as an operation surface) and are configured to detect a change in capacitance corresponding to a touch operation or proximity operation with a finger of an operator between adjacent electrodes as an input operation.
FIG. 13 is a diagram for explaining a conventional capacitive touch panel, which shows an arrangement of sensor electrodes for detecting a change in capacitance due to a touch operation or a proximity operation.
A touch panel 50 has, for example, a plurality of rhombus sensor electrode 51a, 52a and a plurality of triangular sensor electrodes 51b, 52b (hereinafter, also simply referred to as sensor electrodes) arranged in a matrix on an insulation transparent substrate 50a such as a glass substrate or a plastic film. Herein, the sensor electrodes 51a and 51b aligned in a row direction (X direction) are electrically connected by electrode connecting sections 51c to constitute a plurality of row electrodes (X sensors) 51. Further, the sensor electrodes 52a and 52b are electrically connected by electrode connecting sections 52c aligned along the column direction (Y direction) to constitute a plurality of column electrodes (Y sensor) 52. Herein, the triangular sensor electrodes 51b constituting the row electrode 51 are disposed at both ends of the row electrode 51, and the rhombus sensor electrodes 51a are disposed at positions other than both ends of the row electrode 51. Similarly, the triangular sensor electrodes 52b constituting the column electrode 52 are disposed at both ends of the column electrode 52, and the rhombus sensor electrodes 52a are disposed at positions other than the both ends of the column electrode 52. Further, the sensor electrodes 51a and 51b constituting the row electrode 51, and the sensor electrodes 52a and 52b constituting the column electrode 52 are alternately arranged in the longitudinal and transverse directions. The sensor electrodes 51a, 51b, 52a, 52b and the electrode connecting sections 51c and 52c are constituted with a transparent conductive film, such as an ITO (indium tin oxide) film.
For such a capacitive touch panel 50, the region where the row electrode 51 and the column electrode 52 are arranged forms the operation surface. When an operator touches the operation surface with a finger or brings a finger near a certain position on the operation surface, capacitance between the sensor electrodes 51a, 51b constituting the row electrode 51, and the sensor electrodes 52a, 52b constituting the column electrode 52 adjacent thereto would change at the position where the finger touched or was brought near. The position where the finger touched or was brought near on the operation surface is detected as an operation position by this change in capacitance.
In an electronic information equipment equipped with a touch panel as well as a display device, coordinate information indicating a position on a display screen of the display device corresponding to the detected operation position is generated based on the operation position, and information processing corresponding to the input operation is performed based on the coordinate information.
However, an ITO film, which is a transparent conductive film constituting row and column electrodes, has high resistivity that is commonly in several tens of Ω/□. For this reason, when a large touch panel is manufactured, sensitivity of detection with respect to capacitance decreases with the increase in the resistance value between terminals of a row electrode or a column electrode such that it becomes difficult to make such electrodes operate as a touch switch.
Thus, a capacitive touch panel with low resistance row and column electrodes has already been developed by constituting a sensor electrode and an electrode connecting section with a metallic film instead of an ITO film.
Such a touch panel is configured so that transmittance of electrodes is made to be 70% or greater by constituting a rhombus sensor electrode and an electrode connecting section with a meshed conductive layer (hereinafter, also referred to as meshed metallic layer) consisting of copper or copper alloy, whereby a low resistance electrode is realized while maintaining visibility with respect to a display screen of a display device positioned on the rear side of the touch panel.
Meanwhile, a touch panel, in which intersecting row electrodes and column electrodes are formed on a single insulation transparent substrate as in the capacitive touch panel described above, requires a structure for insulating a row electrode and a column electrode at an intersecting section of both electrodes. Thus, the structure of the electrodes is complex, and an electrode forming process requires a step of patterning at least two layers of conductive layers and a step of forming an insulation film for insulating the top and bottom conductive layers.
In view of this, a capacitive touch panel with the following structure has been developed. In the structure, a sensor sheet made by forming a row electrode on an insulation sheet substrate is bonded together with a sensor sheet made by forming a column electrode on an insulation sheet substrate.
FIGS. 14 and 15 are diagrams for explaining such a touch panel with a structure in which two sensor sheets are bonded together as another example of a conventional touch panel. FIG. 14(a) shows an arrangement of electrodes of this touch panel. FIG. 14(b) shows a cross-sectional structure of this touch panel (portion at the A-A′ line in FIG. 14(a)). FIG. 15(a) and FIG. 15(b) show an arrangement of row electrodes and column electrodes constituting each sensor sheet, respectively.
This touch panel 60 has a first sensor sheet 601 made by forming a row electrode (X sensor) 61 with a meshed metallic layer on an insulation sheet substrate 60a consisting of PET or the like, and a second sensor sheet 602 made by forming a column electrode (Y sensor) 62 with a meshed metallic layer on an insulation sheet substrate 60b consisting of PET or the like. The touch panel has a structure in which the sensor sheets 601 and 602 are bonded together with an insulation adhesive 603.
Herein, a meshed metallic layer has a structure in which a plurality of metallic lines extending in one direction intersect a plurality of metallic lines extending in another direction to form a square-shaped mesh pattern. A meshed metallic layer constituting a row electrode and a meshed metallic layer constituting a column electrode have identical structures in terms of design.
The row electrode (X sensor) 61 and the column electrode (Y sensor) 62 have the same arrangement pattern as those in the touch panel 50 using an ITO film for the row electrode 51 and the column electrode 52 shown in FIG. 13. In other words, the row electrode 61 is made by electrically connecting a plurality of rhombus sensor electrodes 61a and triangular sensor electrodes 61b (hereinafter, simply referred to as sensor electrodes) arranged in a matrix on the insulation sheet substrate 60a along the row direction (X direction) with electrode connecting sections 61c. Further, the column electrode 62 is made by electrically connecting a plurality of rhombus sensor electrodes 62a and triangular sensor electrodes 62b arranged in a matrix on the insulation sheet substrate 60b along the column direction (Y direction) with electrode connecting sections 62c. Herein, the triangular sensor electrodes 61b constituting the row electrode 61 are disposed at both ends of the row electrode 61, and the rhombus sensor electrode 61a are disposed at positions other than the both ends of the row electrode 61. Similarly, the triangular sensor electrodes 62b constituting the column electrode 62 are disposed at both ends of the column electrode 62, and the rhombus sensor electrodes 62a are disposed at positions other than the both ends of the column electrode 62.
Such a capacitive touch panel 60 using a meshed metallic layer for row and column electrodes has problems, such as uneven shading appearing on a surface of the touch panel due to dislocation in the bonding of the two sensor sheets, or uneven shading appearing due to a difference in line widths between a metallic line of the meshed metallic layer constituting the row electrode, and a metallic line of the meshed metallic layer constituting the column electrode. Such a difference in line widths of metallic lines occurs due to variability in the process conditions during etching for processing a metallic film in a meshed form.
As a measure against such problems, Patent Literature 1 discloses a touch panel using a whole surface mesh structure which leaves portions that do not function as a row electrode or a column electrode as a dummy electrode instead of a structure which removes portions that do not function as a row electrode or a column electrode from the meshed metallic layers constituting the row and column electrodes in the first and second sensor sheets bonded together (see FIG. 15(a) and FIG. 15(b)), such that the distribution of metallic lines constituting the row electrode or the column electrode is more uniform in each sensor sheet.
FIGS. 16 and 17 are diagrams for explaining the touch panel disclosed in Patent Literature 1. FIG. 16(a) shows an arrangement of electrodes in this touch panel. FIG. 16(b) shows a cross-sectional structure of this touch panel (portion at B-B′ line in FIG. 16(a)). FIGS. 17(a) and 17(b) show an arrangement of row electrodes and column electrodes constituting first and second sensor sheets to be bonded together, respectively.
A touch panel 70 has a first sensor sheet 701 made by patterning a meshed metallic layer formed on an insulation sheet substrate 70a so that a row electrode (X sensor) 71 is formed, and a second sensor sheet 702 made by patterning a meshed metallic layer formed on an insulation sheet substrate 70b so that a column electrode (Y sensor) 72 is formed. The touch panel has a structure in which the sensor sheets 701 and 702 are bonded together with an insulation adhesive 703.
Herein, the column electrode 71 is made by electrically connecting a plurality of rhombus sensor electrodes 71a and triangular sensor electrodes 71b (hereinafter, simply referred to as sensor electrodes) arranged in a matrix on the insulation sheet substrate 70a along the row direction (X direction) with electrode connecting sections 71c. On the insulation sheet substrate 70a, a rhombus dummy electrode 71d and a triangular dummy electrode 71e that are electrically separated from the row electrode 71 are formed such that the dummy electrodes are positioned in a region other than the regions occupied by the sensor electrodes 71a and 71b constituting the row electrode 71. The triangular dummy electrode 71e is disposed on a peripheral edge section of the first sensor sheet 701, and the rhombus dummy electrode 71d is disposed on a region other than the peripheral edge section of the first sensor sheet 701.
Similarly, the column electrode 72 is made by electrically connecting a plurality of rhombus sensor electrodes 72a and triangular sensor electrodes 72b (hereinafter, simply referred to as sensor electrode) arranged in a matrix on the insulation sheet substrate 70b along the column direction (Y direction) with electrode connecting sections 72c. On the insulation sheet substrate 70b, a rhombus dummy electrode 72d and a triangular dummy electrode 72e electrically separated from the column electrode 72 are formed such that the dummy electrodes are positioned in a region other than the regions occupied by the sensor electrodes 72a and 72b constituting the column electrode 72. The triangular dummy electrode 72e is disposed at a peripheral edge section of the second sensor sheet 702, and the rhombus dummy electrode 72d is disposed in a region other than the peripheral edge section of the second sensor sheet 702.
Herein, a meshed metallic layer has the same structure as the meshed metallic layer in the touch panel in which two sensor sheets are bonded together, as explained in FIGS. 14 and 15. In other words, a meshed metallic layer has a structure in which a plurality of metallic lines extending in one direction intersect a plurality of metallic lines extending in another direction to form a square-shaped mesh. A meshed metallic layer constituting a row electrode and a meshed metallic layer constituting a column electrode have identical structures in terms of design.
Further, Patent Literature 2 also discloses a touch panel with a sensor sheet having a whole surface mesh structure as in Patent Literature 1, wherein metallic lines of meshed metallic layers are divided along the contour of a row electrode and a column electrode to form a meshed row electrode and a meshed column electrode.